A hybrid vehicle may include an internal combustion engine and an electric motor to propel the vehicle. The motor may be selectively coupled to the engine via a driveline disconnect clutch. The motor may be used at lower driver demand torque levels while the engine, or engine and motor, may operate at higher driver demand torque levels. If the motor is the sole vehicle torque source providing torque to propel the vehicle, it may be desirable to operate the vehicle driveline as efficiently as possible to extend the vehicle's operating range. One way to increase driveline operating efficiency is to lock a torque converter clutch of a torque converter that may be positioned downstream of the motor and engine and upstream of transmission gears. However, the torque converter dampens driveline torque disturbances and provides torque multiplication when the torque converter clutch is not locked. One type of driveline torque disturbance that may be dampened via the torque converter is transmission gear shifting torque disturbances. Gear shifting torque disturbances may be attenuated via the torque converter if the torque converter clutch is in an open state. However, the driveline efficiency may be reduced if the torque converter clutch is open during transmission gear shifting, thereby reducing the range the motor may propel the vehicle.
The inventors herein have recognized the above-mentioned issues and have developed a driveline operating method, comprising: propelling a vehicle via a motor in a driveline with an open disconnect clutch and a locked torque converter clutch; adjusting a torque output command of the motor via transmission output shaft feedback in response to fixed ratio transmission gear shift; and operating the motor based on the adjusted torque output command.
By adjusting motor torque in response to transmission output shaft acceleration or torque, it may be possible to provide the technical result of reducing driveline torque disturbances during gear shifting of a fixed ratio transmission while a torque converter clutch is locked. In one example, transmission output shaft torque feedback may be a basis for aligning a transmission input torque with closing time of an on-coming clutch. Aligning the transmission input torque with on-coming clutch closing time may reduce driveline torque disturbances due to transmission gear shifting. Further, by holding the torque converter lockup clutch in a closed state, transmission efficiency may be improved. Consequently, it may be possible for the motor to propel the vehicle further when transmission output shaft torque or acceleration is applied as feedback to a transmission input command torque.
The present description may provide several advantages. Specifically, the approach may provide improve vehicle energy efficiency. Additionally, the approach may reduce driveline torque disturbances during transmission gear shifting. Further, the approach may be selectively applied when driveline dampening to reduce engine torque pulsations is not desired.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.